add state query support

lib/routing.js

@@ -46,20 +46,43 @@ const reverseMappings = mappings.map(mapping =>
   })
 )
 
+const serializeState = state => {
+  const stateString = encodeURIComponent(JSON.stringify(state))
+
+  return typeof window !== 'undefined'
+    ? btoa(stateString)
+    : Buffer.from(stateString).toString('base64')
+}
+
+const deserializeState = serializedState => {
+  let stateString
+  if (typeof window !== 'undefined') {
+    stateString = atob(serializedState)
+  } else {
+    stateString = Buffer.from(serializedState, 'base64').toString()
+  }
+
+  return JSON.parse(decodeURIComponent(stateString))
+}
+
 const keysToQuery = keys =>
   `?${Object.keys(keys)
     .map(key => `${key}=${keys[key]}`)
     .join('&')}`
 
 export const getQueryStringState = query => {
-  const state = mapper.map(mappings, query)
-  deserializeCode(state)
+  if (query.state) {
+   return deserializeState(query.state) 
+  } else {
+    const state = mapper.map(mappings, query)
+      deserializeCode(state)
 
-  Object.keys(state).forEach(key => {
-    if (state[key] === '') state[key] = undefined
-  })
+      Object.keys(state).forEach(key => {
+        if (state[key] === '') state[key] = undefined
+      })
 
-  return state
+    return state
+  }
 }
 
 export const updateQueryString = state => {